This invention relates to heat pumps, and in particular to an improvement in the construction of reversible heat pumps of the type that circulate a refrigerant in separate heating and cooling cycles to transfer heat to or from space.
A heat pump is a device that extracts heat from a low temperature source and makes it available as useful heat at a higher temperature. Experimental heat pumps were constructed as early as the mid 1920's, and shortly thereafter heat pumps were used for heating applications. Eventually, heat pumps were developed that were basically reversible air conditioners, having reversible cycles for circulating a refrigerant to selectively transfer heat to or from space. These heat pumps typically comprise a heat exchanger for the addition of or removal of heat from the air forced over it by conducting heat to or from refrigerant circulating therein; a condenser/evaporator coil for the addition of or removal of heat from the refrigerant, and a compressor for circulating the refrigerant through an expansion device. The gas discharge of the compressor is connected to a reversing valve. The reversing valve is connected to the heat exchanger, the condenser/evaporator coil, and the compressor suction gas inlet. The heat exchanger and the condenser/evaporator coil are interconnected with at least one expansion device. In the heating cycle, the reversing valve directs refrigerant gas from the compressor discharge to the heat exchanger. The refrigerant transfers heat by loss to the air forced over the heat exchanger. The liquid refrigerant then passes through an expansion device where it is vaporized and on to the condenser/evaporator coil where the refrigerant absorbs heat. The refrigerant gas returns via the reversing valve to the compressor suction inlet. In the cooling cycle, the reversing valve directs refrigerant gas from the compressor discharge to the condenser/evaporator coil. The refrigerant loses heat to the condenser/evaporator coil and condenses. The liquid refrigerant then passes through an expansion device where it is vaporized and on to the heat exchanger where it absorbs heat from air forced over the heat exchanger. The refrigerant returns via the reversing valve to the compressor suction gas inlet.
In these heat pumps, the refrigerant is frequently contaminated by lubricating oil from the compressor. The presence of the oil impairs the heat transfer properties of the refrigerant, reducing the efficiency of the heat pump. Furthermore, the loss of lubricating oil from the compressor can potentially damage the compressor.